The present invention relates to a binder composition suitable for producing a hot press molded board from a lignocellulose and/or an inorganic material as a main raw material. Also, the present invention relates to a process for producing a hot press molded board from a lignocellulose and/or an inorganic material as a main raw material.
In molded articles made of a lignocellulose as a main raw material, those in which the lignocellulose is a wood chip are called as a particle board Besides the particle board, there are a wafer board made of a large-sized chip and an oriented strand board (OSB) in which long and slender chips (strands) are oriented in a certain direction. Also, those in which the lignocellulose is a wood fiber are called as an insulation board, a hardboard, or a medium-density fiber board (MDF). Further, those made of an inorganic material as a main raw material are produced by using a rock wool or shirasu. These boards are used as a flooring material, a wall material, a door material, a soundproofing material, a heat insulating material, a mat core material, a furniture member, an automobile member, a floor primary material, etc.
As binders for molding a particle board, a wafer board, an OSB, an insulation board, a hardboard, a medium-density fiber board, a rice hull board prepared by molding a rice hull, a kaoliang board prepared by molding a kaoliang stalk, an inorganic board made of an inorganic material as a raw material, and the like (these boards being hereinafter simply referred to as xe2x80x9cboardxe2x80x9d or xe2x80x9cboardsxe2x80x9d), there have hitherto been widely used a thermosetting urea resin, melamine resin, urea-melamine resin, melamine-urea resin, phenol resin, phenol-melamine resin, melamine-phenol resin, etc. (these binders being hereinafter simply referred to as xe2x80x9cformaldehyde-based binderxe2x80x9d or xe2x80x9cformaldehyde-based bindersxe2x80x9d). The formaldehyde-based binders have such characteristics that they are inexpensive, are superior in adhesion and are set within a relatively short period of time. However, it is being demanded that the amount of formaldehyde released from products obtained by hot press molding by using a formaldehyde-based binder is further reduced. As countermeasures for reducing the amount of formaldehyde to be released, there have hitherto been employed a method in which the amount of free formaldehyde in a formaldehyde binder is reduced (a molar ratio of formaldehyde to phenol, melamine or urea in the formaldehyde-based binder is lowered) and a method in which a formaldehyde catcher (scavenger) is added at the time of compounding of the formaldehyde-based binder. Also, there has been proposed a use of a non-formaldehyde-based binder (for example, an isocyanate-based binder).
However, in case that the hot press molding is carried out by using an isocyanate-based binder as the binder for a hot press molded board, attachment of the binder to a hot press surface (platen) (metal) occurs due to its excellent adhesion. As a result, it takes much labors to remove attached materials from the hot board.
In order to solve this problem, additives to organic polyisocyanates for improving the releasability from the metal (these additives being referred to as xe2x80x9cinternal releasing agentxe2x80x9d or xe2x80x9cinternal releasing agentsxe2x80x9d) are being investigated. For example, there are proposed alkyl phosphates or pyrophosphates, sulfonated compounds, waxes and liquid esters, aliphatic carboxylic acids, montan waxes and/or carnauba waxes, and the like as additives to organic polyisocyanates. In addition, the present applicant has proposed metal soaps of a fatty acid as a releasing agent effective for urethane compounds.
Also, as another method, there has been proposed a method in which a releasing agent is applied directly to a hot press surface (platen) prior to the hot pressing (such releasing agent being referred to as xe2x80x9cexternal releasing agentxe2x80x9d). For example, there are a method in which a release layer using a metal soap is formed and a method in which a polysiloxane film having a functional group is used.
However a binder which is superior in physical property to that obtained by the above-described methods and which can be used for longer period is desired.
An object of the invention is to provide, in the preparation of a hot press molded board from a lignocellulose or an inorganic material as a main raw material, an isocyanate-based binder composition with which a board having eternally good releasability from a hot press plate, excellent physical properties and low hygroscopicity can be obtained with improved productivity.
The present inventors have made extensive and intensive studies on a binder composition suitable for producing a hot press molded board from a lignocellulose or an inorganic material as a main raw material. As a result, it has been found that it is effective to contain a compound having at least two isocyanate groups or its reaction product and a low-molecular weight polyethylene as essential components in the binder composition, leading to the accomplishment of the present invention. Also, it has been found that in a process for producing a hot press molded board from a lignocellulose or an inorganic material as a main raw material, when a low-molecular weight polyethylene is used as a releasing agent component to be used in the binder, eternally good releasability from a hot press surface (platen) is obtained, leading to achievement of the present invention.
That is, the present invention is to provide the following (1) to (24).
(1) A binder composition comprising:
(A) a compound having at least two isocyanate groups or its reaction product,
(B) a low-molecular weight polyethylene, and
(C) water.
(2) A binder composition as set forth in (1), wherein a weight ratio of the compound having at least two isocyanate groups or its reaction product (A) to the low-molecular weight polyethylene (B) is from 1:0.001 to 1:1.
(3) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has a number average molecular weight (MN) by gel permeation chromatography (GPC) of from 500 to 7,000 in terms of monodispersed polystyrene.
(4) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has a number average molecular weight (MN) by gel permeation chromatography of from 1,000 to 6,000 in terms of monodispersed polystyrene.
(5) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has a ratio of weight average molecular weight (MW) to number average molecular weight (MN) by gel permeation chromatography is from 1.2 to 3.0.
(6) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has a ratio of weight average molecular weight (MW) to number average molecular weight (MN) by gel permeation chromatography is from 1.5 to 3.0.
(7) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has a branching structure.
(8) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has a density of from 0.800 to 0.980.
(9) A binder composition as set forth in (8), wherein the low-molecular weight polyethylene (B) has a density of from 0.800 to 0.925.
(10) A binder composition as set forth in (8), wherein the low-molecular weight polyethylene (B) has a functional group selected from xe2x80x94OH, xe2x80x94COOH, or xe2x80x94CHO and has a density exceeding 0.940.
(11) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has an endothermic peak by a differential scanning calorimeter (DSC) at from 30xc2x0 C. to 120xc2x0 C.
(12) A binder composition as set forth (1) or (2), wherein the low-molecular weight polyethylene (B) has an endothermic peak by a differential scanning calorimeter (DSC) at from 40xc2x0 C. to 100xc2x0 C.
(13) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has at least three methyl group carbon atoms per 100 carbon atoms in the low-molecular weight polyethylene (B).
(14) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) has at least four methyl group carbon atoms per 100 carbon atoms in the low-molecular weight polyethylene (B).
(15) A binder composition as set forth in (1) or (2), wherein the low-molecular weight polyethylene (B) is used as an aqueous emulsion or suspension comprising the water (C) as a dispersion medium.
(16) A binder composition as set forth in (15), wherein the aqueous emulsion or suspension of the low-molecular weight polyethylene (B) comprising the water (C) as a dispersion medium has a mean particle size of from 100 to 10,000 nm.
(17) A binder composition as set forth in (1) or (2), wherein the compound having at least two isocyanate groups or its reaction product (A) comprises a reaction product of (D) a monofunctional alcohol having from 80 to 99% by weight of a recurring unit of (xe2x80x94CH2CH2xe2x80x94Oxe2x80x94) and a compound having at least two isocyanate groups.
(18) A binder composition as set-forth in (1) or (2), wherein the compound having at least two isocyanate groups or its reaction product (A) is emulsified or dispersed in water by using (E) a bifunctional to octafunctional polyol having from 5 to 70% by weight of a recurring unit of (xe2x80x94CH2CH2xe2x80x94Oxe2x80x94) in the structure thereof.
(19) A binder composition as set forth in (18), wherein the compound having at least two isocyanate groups or its reaction product (A), the low-molecular weight polyethylene (B), the water (C), and the polyol (E) are formed in an aqueous dispersion by using an in-line mixer and then used.
(20) A binder composition as set forth in (1) or (2), wherein the compound having at least two isocyanate groups or its reaction product (A) is polymethylene polyphenyl diisocyanate (polymeric MDI).
(21) A process for the production of a board by using a lignocellulose-based material and a binder, wherein the binder is a binder composition as set forth in any one of (1) to (20).
(22) A process for the production of a board by using an inorganic material and a binder, wherein the binder is a binder composition as set forth in any one of (1) to (20).
(23) A board obtained by a process as set forth in (21).
(24) A board obtained by a process as set forth in (22).